Apple also has been writing drivers for a number of popular sound and video cards. On the audio front, clear changes are underway. The OS X group has identified that users want higher-resolution 24-bit audio, with a 196 KHz sampling rate. With the release of 10.2.3, support was added for SoundBlaster Extigy, and as of last month, work was nearly complete on Audigy and Audigy 2 drivers. This may be present in 10.2.4, but if it isn't slipped in, it will certainly be a part of the v10.3 Panther upgrade. Initial support for Audigy 2 will probably be limited at best, however.

I can confirm it. A friend over at neowin is using his Extigy with his Mac as week speak. Apparently there's no 5.1 support or he just can't get it to work. But all he did was plug the usb cable in and OSX saw it.